1. Field of the Invention
The invention relates to a tire pressure indicator, more particularly to one including pressure gauges that have a self-generating power capability.
2. Description of the Related Art
A tire pressure indicator is to be installed in a vehicle to monitor the pressure of the tires of the vehicle. A regular tire pressure indicator is generally comprised of a set of pressure gages, each of which is mounted on a corresponding pneumatic tire of the vehicle, and a receiver device. Each pressure gauge wirelessly transmits a pressure signal to the receiver device when the pressure in the corresponding pneumatic tire is not within a predetermined normal operating pressure range. As such, the receiver device can alert the driver of the vehicle in the event of an abnormal tire pressure condition.
Since the receiver device of a known tire pressure indicator is built into an instrument panel of the vehicle, or as a separate device to be installed in the driver's compartment of the vehicle, the power source of the vehicle can be used as the power source for the receiver device. However, since the pressure gauges of the known tire pressure indicator are mounted on the tires of the vehicle, battery cells are used as the power source for the pressure gauges. The need to replace the battery cells when they run out of power inconveniences the owner of the vehicle.
In order to eliminate the aforesaid problem, the same applicant filed an application for a tire pressure indicator, which subsequently issued as U.S. Pat. No. 5,694,111. The structure of this tire pressure indicator comprises a piezoelectric type self-generating voltage means, and an LC oscillatory loop formed of a volume variable member, a magnetic core, and an induction coil. This structure of the tire pressure indicator is functional, however, the installation cost of the LC oscillatory loop is expensive.